In recent years, for using a clean energy, public attention is attracted to a technology utilizing hydrogen in fuel battery and heat pump, and in the storage of a natural energy, etc. In these hydrogen utilizing technologies, hydrogen storage alloys are conventionally used in order to conduct the occlusion and release of hydrogen. However, these hydrogen storage alloys have drawbacks that they are heavy in weight, and when the occlusion/release process is repeated, material degradation occurs and exhibit decreased hydrogen storage capability (deterioration of the repeated properties).
Under such circumstances, a technology has been recently studied which utilizes a carbon-type material such as carbon nanotube, graphite nanofiber, etc. wherein hydrogen is occluded in a void caused from the crystal defect, layer structure etc. of the carbon structure. Particularly, attention is currently focused on amorphous carbon materials which are generally said to exhibit little deterioration of the repeated properties of the hydrogen occlusion/release as described above (for example, refer to Unexamined Japanese Patent Publications(Kokai) 2001-106516 and 2002-28483).
However, even if these carbon materials are used, it must be said that the improvement of the repeated hydrogen occlusion/release properties are not still satisfactory. This is believed to be attributable to the fact that the hydrogen storage site (the site in which hydrogen is retained) and the adsorption/release site (the site in which hydrogen migration occurs with the desorption of hydrogen from the hydrogen storage site) are on the identical place, and therefore the carbon structure breaks down and changes due to the repeated occlusion/release process.